Portions of Arctic coastline eroding, no end in sight

A new study led by the University of Colorado at Boulder indicates part of the northern Alaska coastline is eroding by up to 45 feet annually due to declining sea ice, warming seawater and increased wave activity. -  Robert S. Anderson, University of Colorado
A new study led by the University of Colorado at Boulder indicates part of the northern Alaska coastline is eroding by up to 45 feet annually due to declining sea ice, warming seawater and increased wave activity. – Robert S. Anderson, University of Colorado

The northern coastline of Alaska midway between Point Barrow and Prudhoe Bay is eroding by up to one-third the length of a football field annually because of a “triple whammy” of declining sea ice, warming seawater and increased wave activity, according to new study led by the University of Colorado at Boulder.

The conditions have led to the steady retreat of 30 to 45 feet a year of the 12-foot-high bluffs — frozen blocks of silt and peat containing 50 to 80 percent ice — which are toppled into the Beaufort Sea during the summer months by a combination of large waves pounding the shoreline and warm seawater melting the base of the bluffs, said CU-Boulder Associate Professor Robert Anderson, a co-author on the study. Once the blocks have fallen, the coastal seawater melts them in a matter of days, sweeping the silty material out to sea.

Anderson, along with collaborators Cameron Wobus of Stratus Consulting and Irina Overeem of CU’s Institute of Arctic and Alpine Research, or INSTAAR, each presented results from components of their study at the annual meeting of the American Geophysical Union in San Francisco held Dec. 14-18.

The problem is caused by several factors, including increased erosion along the Alaskan coastline due to longer ice-free summer conditions and warmer seawater bathing the coast, Anderson said. The third potential factor is that the longer the sea ice is detached from the coastline, the further out to sea the sea-ice edge will be. This open-ocean distance between the sea ice and the shore, known as the “fetch,” increases both the energy of waves crashing into the coast and the height to which warm seawater can come into contact with the frozen bluffs, said Anderson.

“What we are seeing now is a triple whammy effect,” said Anderson. “Since the summer Arctic sea ice cover continues to decline and Arctic air and sea temperatures continue to rise, we really don’t see any prospect for this process ending.”

In addition to Wobus and Overeem, co-authors on the studies include Gary Clow and Frank Urban of the U.S. Geological Survey in Lakewood, Colo., and Tim Stanton of the Naval Postgraduate School in Monterey, Calif.

The shoreline bluffs are made up of contiguous, polygon-shaped blocks, primarily made of permafrost and each roughly 70 to 100 feet across, he said. Ice “wedges” created by seeping summer surface water that annually freezes and thaws are driven deeper and deeper into the cracks between individual blocks each year. The blocks closest to the sea are undermined as warm seawater melts their base, and eventually split apart from neighboring blocks and topple during stormy conditions, said Anderson.

The researchers used a variety of instruments and methods in the study to examine the dynamic transition between the land and the sea, including time-lapse photography of shoreline erosion, global positioning systems (GPS), meteorological measurements including temperature and wind speed, and sediment analysis of the coastal bluffs. Offshore measurements included sea-ice distribution, ocean floor depth, sea-surface temperatures and wave dynamics, said Anderson, also a fellow at INSTAAR.

The time-lapse images were taken with four tripod mounted “game cameras” often used by hunters and wildlife biologists and which were set up parallel to the shoreline. The cameras snapped pictures every six hours during the 24-hour summer daylight months to track the effects of the waves on the coastline, said Anderson.

“Once one of these blocks topples, the process continues on to the next block,” Anderson said. “These images are very powerful, because they pick up activity during severe storms when we aren’t there to watch.” The images also illustrate the steady melting along the water’s edge that helps to undermine the bluffs even in the absence of storm activity.

The research team also deployed four submerged ocean buoys attached to metal sleds with sensors to measure the wave activity at different depths in the shallow coastal waters, comparing wave power with the shoreline fetch. The team attached temperature sensors to the buoy mooring lines to monitor seawater temperatures, which have been warming in recent summers due to increased solar radiation, he said.

When the sea ice is further from the shore, currents from the Beaufort and Chukchi seas transport warmer water to the coastline, said Anderson. While the temperature hovers around 45 degrees during the summer months, the shallow coastal water warmed to as much as 59 degrees during the 2007 field season — the same year the largest loss of summer Arctic sea was recorded, he said.

As the ice wedges cut down through the polygon blocks, the surface soil above them — which thaws each summer — is pushed up slightly, forming small ridges that eventually surround each polygon, said Anderson. Small ponds form above individual polygons during the summer months as the surface ice and snow melts, providing habitat for migrating birds that feed and breed along the Beaufort Sea coastline.

“This is an important habitat for birds and other wildlife,” said Anderson. “One of the concerns we have is that some larger ponds and lakes located slightly further inland may begin draining into the sea as the shoreline continues to recede.”

While there are no towns adjacent to the specific study area, coastal erosion threatens abandoned military and petroleum infrastructure, he said. Coastal erosion occurs at similar sites elsewhere along Alaska’s coastline. Bank stabilization measures using sandbags, for example, have been undertaken at the Alaskan town of Kaktovik on the Beaufort Sea in an attempt to slow the problem.

According to a 2009 CU-Boulder study, Arctic sea ice during the annual September minimum is now declining at a rate of 11.2 percent per decade. Only 19 percent of the ice cover was more than two years old — the least ever recorded in the satellite record and far below the 1981-2000 summer average of 48 percent.

Sun and moon trigger deep tremors on San Andreas Fault

When the sun and moon are aligned with the San Andreas Fault they tug on it enough to increase the tremor rate deep underground, according to a new UC Berkeley study. While these tremors have not yet been linked to earthquakes, the tremors are associated with increased stress on the fault and may increase the risk of future quakes. The ease with which the deep rock slips indicates it is lubricated by high-pressure water.
When the sun and moon are aligned with the San Andreas Fault they tug on it enough to increase the tremor rate deep underground, according to a new UC Berkeley study. While these tremors have not yet been linked to earthquakes, the tremors are associated with increased stress on the fault and may increase the risk of future quakes. The ease with which the deep rock slips indicates it is lubricated by high-pressure water.

The faint tug of the sun and moon on the San Andreas Fault stimulates tremors deep underground, suggesting that the rock 15 miles below is lubricated with highly pressurized water that allows the rock to slip with little effort, according to a new study by University of California, Berkeley, seismologists.

“Tremors seem to be extremely sensitive to minute stress changes,” said Roland Bürgmann, UC Berkeley professor of earth and planetary science. “Seismic waves from the other side of the planet triggered tremors on the Cascadia subduction zone off the coast of Washington state after the Sumatra earthquake last year, while the Denali earthquake in 2002 triggered tremors on a number of faults in California. Now we also see that tides – the daily lunar and solar tides – very strongly modulate tremors.”

In a paper appearing in the Dec. 24 issue of the journal Nature, UC Berkeley graduate student Amanda M. Thomas, seismologist Robert Nadeau of the Berkeley Seismological Laboratory and Bürgmann argue that this extreme sensitivity to stress – and specifically to shearing stress along the fault – means that the water deep underground is under extreme pressure.

“The big finding is that there is very high fluid pressure down there, that is, lithostatic pressure, which means pressure equivalent to the load of all rock above it, 15 to 30 kilometers (10 to 20 miles) of rock,” Nadeau said. “Water under very high pressure essentially lubricates the rock, making the fault very weak.”

Though tides raised in the Earth by the sun and moon are not known to trigger earthquakes directly, they can trigger swarms of deep tremors, which could increase the likelihood of quakes on the fault above the tremor zone, the researchers say. At other fault zones, such as at Cascadia, swarms of tremors in the ductile zone deep underground correlate with slip at depth as well as increased stress on the shallower “seismogenic zone,” where earthquakes are generated. The situation on the San Andreas Fault is not so clear, however.

“These tremors represent slip along the fault 25 kilometers (15 miles) underground, and this slip should push the fault zone above in a similar pattern,” Bürgmann said. “But it seems like it must be very subtle, because we actually don’t see a tidal signal in regular earthquakes. Even though the earthquake zone also sees the tidal stress and also feels the added periodic behavior of the tremor below, they don’t seem to be very bothered.”

Nevertheless, said Nadeau, “It is certainly in the realm of reasonable conjecture that tremors are stressing the fault zone above it. The deep San Andreas Fault is moving faster when tremors are more active, presumably stressing the seismogenic zone, loading the fault a little bit faster. And that may have a relationship to stimulating earthquake activity.”

Seismologists were surprised when tremors were first discovered more than seven years ago, since the rock at that depth – for the San Andreas Fault, between 15 and 30 kilometers (10 to 20 miles) underground – is not brittle and subject to fracture, but deformable, like peanut butter. They called them non-volcanic tremors to distinguish them from tremors caused by fluid – water or magma – fracturing and flowing through rock under volcanoes. It was not clear, however, what caused the non-volcanic tremors, which are on the order of a magnitude 1 earthquake.

To learn more about the source of these tremors, UC Berkeley seismologists began looking for tremors five years ago in seismic recordings from the Parkfield segment of the San Andreas Fault obtained from sensitive bore-hole seismometers placed underground as part of the UC Berkeley’s High-Resolution Seismic Network. Using eight years of tremor data, Thomas, Bürgmann and Nadeau correlated tremor activity with the effects of the sun and moon on the crust and with the effects of ocean tides, which are driven by the moon.

They found the strongest effect when the pull on the Earth from the sun and moon sheared the fault in the direction it normally breaks. Because the San Andreas Fault is a right-lateral strike-slip fault, the west side of the fault tends to break north-northwestward, dragging Los Angeles closer to San Francisco.

“When shear stress on a plane parallel to the San Andreas Fault most encourages slipping in its normal slip direction is when we see the maximum tremor rate,” Bürgmann said. “The stress is many, many orders of magnitude less than the pressure down there, which was really, really surprising. You essentially could push it with your hand and it would move.”

In fact, the shear stress from the sun, moon and ocean tides amount to around 100 Pascals, or one-thousandth atmospheric pressure, whereas the pressure 25 kilometers underground is on the order of 600 megaPascals, or 6 million times greater.

Nadeau and colleagues reported earlier this year that earthquakes in 2003 and 2004 near the Parkfield segment of the San Andreas Fault increased both tremor activity and stress on the fault itself.

In addition, Nadeau noted, other scientists have shown small tidal effects on tremors in the Cascadia subduction zone, with increased amplitude during certain periods, though they were unable to distinguish between tugs along the fault and tugs across, or normal to, the fault.

“We were really able to tighten the nuts down on whether it is a normal-fault stress change or an along-fault stress change that is stimulating the tremor,” he said. The fact that tremors are triggered by along-fault shear stress “means that fluids are probably the explanation.”

It may be that tremors only occur on faults where fluid is trapped deep underground with no cracks or fractures allowing it to squirt away, Nadeau added. That may explain why tremors are not observed on other faults, despite intense searching.

“There is still all lot to learn about tremor and earthquakes in fault zones,” he said. “The fact that we find tremors adjacent to a locked fault, like the one at Parkfield, makes you think there are some more important relationships going on here, and we need to study it more.”

Formation of the Gulf of Corinth rift, Greece

This is the view to the west along the Gulf of Corinth active rift showing the bathymetry of the seafloor within the active offshore rift and a cross section beneath the seafloor interpreted from a seismic reflection profile. Red dashed lines on the seafloor and on the coast to the south are the major normal faults which control the region's morphology and the opening of the rift. Colored layers within the cross section represent layers of sediment deposited and deformed as the rift subsides. -  NOCS
This is the view to the west along the Gulf of Corinth active rift showing the bathymetry of the seafloor within the active offshore rift and a cross section beneath the seafloor interpreted from a seismic reflection profile. Red dashed lines on the seafloor and on the coast to the south are the major normal faults which control the region’s morphology and the opening of the rift. Colored layers within the cross section represent layers of sediment deposited and deformed as the rift subsides. – NOCS

A study of the structure and evolution of the Gulf of Corinth rift in central Greece will increase scientific understanding of rifted margin development and the tectonic mechanisms underlying seafloor spreading and deformation of the Earth’s crust.

“The Gulf of Corinth rift is an ideal natural laboratory for studying early rift history,” said Dr Lisa McNeill of the University of Southampton’s School of Ocean and Earth Science (SOES) at the National Oceanography Centre, Southampton (NOCS): “The rift is less than five million years old and is relatively easy to interpret as its structure has not been significantly complicated by geological events over a long period of time. The rifting process is also the source of hazardous earthquakes in the region”

Using available marine and terrestrial data, including high-resolution seismic reflection profiles from a research cruise aboard the MV Vasilios in 2003, the researchers analysed fault evolution across the entire rift system, producing a fault framework for the rift and revealing patterns of basin subsidence through rift history. They also estimated when faults became active and the rates at which they slip.

“Our analysis shows how the system of faults associated with the Corinth rift has evolved over time, which can now be compared with other rifts worldwide and with computer models of rift development,” said Dr Rebecca Bell, former SOES PhD student at the National Oceanography Centre, now working at GNS Science, New Zealand and lead author of the research.

The Corinth rift is about 100 kilometres long and 30 kilometers wide. It is under high strain, its north and south sides separating due to tectonic forces by up to ~15 milimetres per year.

The researchers find that the rift has undergone major changes in fault activity and the shape of the rift basin during its short history. The currently active Gulf of Corinth Basin is thought to have formed only 1-2 million years ago.

Before around 400,000 years ago, two separate areas of sediment deposition or basins (20-50 kilometres long) were created, controlled by north- and south-dipping faults. Since this time, these basins have coalesced into one (80 kilometres long) controlled by multiple connected faults.

The researchers conclude that isolated but nearby faults can persist for around a million years and form major basins before becoming linked deep below the Earth’s surface: “Basin subsidence and the eventual transition to seafloor spreading are controlled by the development and interaction of fault systems established in the early stages of continental rifting.”

New computer program to give students experience with geosciences’ data

The National Science Foundation recently awarded a grant of $144,244 to Williams College to fund a project titled “Visualizing Strain in Rocks with Interactive Computer Programs.” The project is under the direction of Paul Karabinos, professor and chair of the geosciences department.

Karabinos’ project emphasizes the importance of strain in structural geology and seeks to develop computer programs to view and analyze strain. Strain is a fundamental topic in structural geology in understanding the development and formation of rocks in folds and fault zones. The exercises will provide an opportunity for students to critically examine the assumptions and limitations of any attempt to quantify natural process.

The program with its tutorials will improve undergraduate courses in structural geology, fostering a deeper understanding of how commonly used strain methods work.

“Virtually every undergraduate geology program offers a course in structural geology,” explains Karabinos. “A successful structural geology course should give students first-hand experience in gathering and analyzing data.”

Karabinos is currently studying a number of western New England sites, including the Chester Dome, Shelburne Falls, and the Berkshire massif and his new grant also supports addition of a computer application to this research.

He is the author of numerous research papers and has presented his work at the Geological Society of America and the New England Intercollegiate Geologic Conference.

He joined the Williams faculty in 1983 and teaches a range of course offerings, including Structural Geology, Geology of the Appalachians, and How Do Mountains Form?

Karabinos received his bachelor’s degree from the University of Connecticut and his Ph.D. from Johns Hopkins University. He did his postdoctoral work at Harvard.

System developed to detect plastic anti-personnel mines

This is a US soldier practicing placing a claymore anti-personnel mine. -  Sgt. Thomas Kielbasa
This is a US soldier practicing placing a claymore anti-personnel mine. – Sgt. Thomas Kielbasa

A team of European researchers has devised a method for locating plastic anti-personnel mines, which are manufactured to avoid detection by metal detectors. The technique involves analyzing the temperature of the ground in three dimensions using specific software and hardware, according to a study published in the journal Computers & Geosciences.

“Detecting anti-personnel mines is a very important and costly area of humanitarian work, and uncovering plastic mines is particularly hard, because they cannot be located using metal detectors, although there are alternatives”, Fernando Rafael Pardo Seco, a researcher at the Electronic Technology Department of the University of Valladolid, tells SINC.

“Nowadays, nearly all anti-personnel mines are plastic, or have only a very small metal content, while anti-tank mines, which are larger, still have a significant metal content”, explains the scientist.

Pardo Seco has incorporated a detection algorithm into a hardware platform, which has been developed by Paula López, a researcher at the University of Santiago de Compostela. Other researchers from the Galician university and others from the University of La Sapienza, Italy, also took part in the study, which has been published in Computers & Geosciences.

The temperatures of the plastic mine and the ground are very different, and although it is very difficult to measure thermal variations at computational level, the scientists have managed to find the right formula for doing so.

The team has applied an own software written with specific programming languages for this task (Handel-C and VHDL) to a programmable semiconductor device known as a Field Programmable Gate Array (FPGA).

The technique makes it possible to generate 3D thermal maps of the ground, making it easier to detect mines, and permitting a 34-fold reduction in the number of calculations required to measure the thermal variations compared with other systems available. “This gives us much greater speed than normal programs on a personal computer, helping to facilitate the application of this system on the ground”, stresses Pardo Seco.

The new method is a non-destructive evaluation technique, part of an interdisciplinary field of study focused on developing technologies to quantitatively classify materials and structures in a non-invasive way. These can be applied for anything from non-invasive medical diagnoses and examinations to the detection of faults within parts in an assembly line.

Hypoxia increases as climate warms

A new study of Pacific Ocean sediments off the coast of Chile has found that offshore waters experienced systematic oxygen depletion during the rapid warming of the Antarctic following the last 'glacial maximum' period 20,000 years ago.
A new study of Pacific Ocean sediments off the coast of Chile has found that offshore waters experienced systematic oxygen depletion during the rapid warming of the Antarctic following the last ‘glacial maximum’ period 20,000 years ago.

A new study of Pacific Ocean sediments off the coast of Chile has found that offshore waters experienced systematic oxygen depletion during the rapid warming of the Antarctic following the last “glacial maximum” period 20,000 years ago.

The findings are intriguing as scientists are exploring whether climate change may be contributing to outbreaks of hypoxia – or extremely low oxygen levels – along the near-shore regions of South America and the Pacific Northwest of the United States.

Results of the study, by researchers at Oregon State University, are being published this week in Nature Geoscience. It builds on a series of field studies by researchers at OSU begun more than a decade ago through the Ocean Drilling Program, led by chief scientist Alan Mix, one of the study’s authors.

The researchers focused their study on the influence of Antarctic Intermediate Water, a huge water mass that extends outward from the Antarctic, infusing Southern Hemisphere oceans with cold, highly oxygenated water – and extending all the way to the Northern Hemisphere.

Climate models suggest that these intermediate waters should have had higher concentrations of oxygen during the last glacial period, but scant evidence backed those assertions. However, the OSU researchers were able to use core samples through the Ocean Drilling Program to analyze sediments from three sites off the Chilean coast to calculate the dissolved oxygen on the seafloor.

They measured levels of manganese and rhenium to reconstruct oxygen levels, which they found began decreasing about 17,000 years ago, as warming accelerated and Antarctic glaciers began to recede.

“When there are high levels of oxygen in the water, there are higher levels of manganese in the sediments,” said Jesse M. Muratli, a master’s student in OSU’s College of Oceanic and Atmospheric Sciences and lead author on the Nature Geosciences study. “Rhenium is just the opposite. In highly oxygenated water, it become soluble and tends to dissolve. Together, they help paint a clear picture of oxygen levels.”

The researchers say the waters off Chile could have become less oxygenated through two mechanisms – a reduction in the size and scope of the Antarctic Intermediate Water during warming associated with the end of the last ice age, or if those waters simply became less oxygenated.

“The water mass forms at the surface where it becomes enriched in oxygen,” said study co-author Zanna Chase, an assistant professor of marine geochemistry at OSU. “Cold weather and wind saturate the water with oxygen and if it gets cold enough, it sinks and this tongue of cold water begins extending northward. Warmer temperatures could restrict oxygen penetration into the Antarctic Intermediate Water, or reduce the production of the water mass.”

Mix said the position of mid-latitude winds, known as the Westerlies, plays a key role in the formation of these subsurface water masses. In a previous study, he and his colleagues documented movement of these wind belts, based on pollen from land and marine microfossils.

“These wind movements closely track the history of water mass oxygenation,” Mix pointed out.

It is not yet clear what effect the findings may have on understanding of the offshore hypoxia events experienced intermittently in the Pacific Northwest over the past eight years. Other researchers from Oregon State University have documented patterns of low-oxygen waters – especially off the central Oregon coast. The worst of these happened in 2006, when oxygen in near-shore waters dipped almost to zero, killing thousands of crabs and other bottom-dwelling creatures.

Similar events occur annually off central Chile and the OSU research group is working with Chilean scientists to compare the two systems.

Changing wind patterns appear to be to blame for the 21st-century hypoxia – and wind may have played a role 20,000 years ago as well. Previous studies by Mix of sediment cores off Oregon revealed more oxygenation of subsurface waters during the last Glacial Maximum – and, as warming followed the last ice age, the Pacific Northwest region also experienced intervals of hypoxia, he said.

“Although this is similar to the effects off Chile, the impacts off Oregon were linked to regional ocean productivity,” Mix said. “These contrasts underscore the importance of studying more than one system. Their differences and similarities allow us to understand the complexity of the ocean and its role in climate change – both in the past, and likely in the future.”

Marine scientists discover deepest undersea erupting volcano

An explosion at the West Mata Volcano throws ash and rock, with molten lava glowing below. -  NSF/NOAA
An explosion at the West Mata Volcano throws ash and rock, with molten lava glowing below. – NSF/NOAA

Scientists funded by the National Science Foundation (NSF) and NOAA have recorded the deepest erupting volcano yet discovered–West Mata Volcano–describing high-definition video of the undersea eruption as “spectacular.”

“For the first time we have been able to examine, up close, the way ocean islands and submarine volcanoes are born,” said Barbara Ransom, program director in NSF’s Division of Ocean Sciences. “The unusual primitive compositions of the West Mata eruption lavas have much to tell us.”

The volcanic eruption, discovered in May, is nearly 4,000 feet below the surface of the Pacific Ocean, in an area bounded by Fiji, Tonga and Samoa.

“We found a type of lava never before seen erupting from an active volcano, and for the first time observed molten lava flowing across the deep-ocean seafloor,” said the expedition’s chief scientist Joseph Resing, a chemical oceanographer at the University of Washington.

“It was an underwater Fourth of July, a spectacular display of fireworks nearly 4,000 feet deep,” said co-chief scientist Bob Embley, a marine geologist at NOAA’s Pacific Marine Environmental Laboratory in Newport, Ore.

“Since the water pressure at that depth suppresses the violence of the volcano’s explosions, we could get an underwater robot within feet of the active eruption. On land, or even in shallow water, you could never hope to get that close and see such great detail.”

Imagery includes large molten lava bubbles three feet across bursting into cold seawater, glowing red vents exploding lava into the sea, and the first-observed advance of lava flows across the deep-ocean floor.

Sounds of the eruption were recorded by a hydrophone and later matched with the video footage.

Expedition scientists released the video and discussed their observations at a Dec. 17 news conference at the American Geophysical Union (AGU)’s annual fall meeting in San Francisco.

The West Mata Volcano is producing boninite lavas, believed to be among the hottest on Earth in modern times, and a type seen before only on extinct volcanoes more than one million years old.

University of Hawaii geochemist Ken Rubin believes that the active boninite eruption provides a unique opportunity to study magma formation at volcanoes, and to learn more about how Earth recycles material where one tectonic plate is subducted under another.

Water from the volcano is very acidic, with some samples collected directly above the eruption, the scientists said, as acidic as battery acid or stomach acid.

Julie Huber, a microbiologist at the Marine Biological Laboratory, found diverse microbes even in such extreme conditions.

Tim Shank, a biologist at the Woods Hole Oceanographic Institution (WHOI), found that shrimp were the only animals thriving in the acidic vent water near the eruption. Shank is analyzing shrimp DNA to determine whether they are the same species as those found at seamounts more than 3,000 miles away.

The scientists believe that 80 percent of eruptive activity on Earth takes place in the ocean, and that most volcanoes are in the deep sea.

Further study of active deep-ocean eruptions will provide a better understanding of oceanic cycles of carbon dioxide and sulfur gases, how heat and matter are transferred from the interior of the Earth to its surface, and how life adapts to some of the harshest conditions on Earth.

The science team worked aboard the University of Washington’s research vessel Thomas Thompson, and deployed Jason, a remotely-operated vehicle owned by WHOI.

Jason collected samples using its manipulator arms, and obtained imagery using a prototype still and HD imaging system developed and operated by the Advanced Imaging and Visualization Lab at WHOI.

Pollution alters isolated thunderstorms

Under certain conditions, pollution can either strengthen or weaken thunderstorm clouds. PNNL researchers have figured out how to factor the effect into climate models. -  UCAR/Carlyle Calvin
Under certain conditions, pollution can either strengthen or weaken thunderstorm clouds. PNNL researchers have figured out how to factor the effect into climate models. – UCAR/Carlyle Calvin

New climate research reveals how wind shear — the same atmospheric conditions that cause bumpy airplane rides — affects how pollution contributes to isolated thunderstorm clouds. Under strong wind shear conditions, pollution hampers thunderhead formation. But with weak wind shear, pollution does the opposite and makes storms stronger.

The work improves climate scientists’ understanding of how aerosols — tiny unseen particles that make up pollution — contribute to isolated thunderstorms and the climate cycle. How aerosols and clouds interact is one of the least understood aspects of climate, and this work allows researchers to better model clouds and precipitation.

“This finding may provide some guidelines on how man-made aerosols affect the local climate and precipitation, especially for the places where ‘afternoon showers’ happen frequently and affect the weather system and hydrological cycle,” said atmospheric scientist Jiwen Fan of the Department of Energy’s Pacific Northwest National Laboratory. “Aerosols in the air change the cloud properties, but the changes vary from case to case. With detailed cloud modeling, we found an important factor regulating how aerosols change storms and precipitation.”

Fan will discuss her results Thursday, December 17 at the 2009 American Geophysical Union meeting. Her study uses data from skies over Australia and China.

The results provide insight into how to incorporate these types of clouds and conditions into computational climate models to improve their accuracy.

A Model Sky

Deep convective clouds reflect a lot of the sun’s energy back into space and return water that has evaporated back to the surface as rain, making them an important part of the climate cycle. The clouds form as lower air rises upwards in a process called convection. The updrafts carry aerosols that can seed cloud droplets, building a storm.

Previous studies produced conflicting results in how aerosols from pollution affect storm development. For example, in some cases, more pollution leads to stronger storms, while in others, less pollution does. Fan and her colleagues used computer simulations to tease out what was going on. Of concern was a weather phenomenon known as wind shear, where horizontal wind speed and direction vary at different heights. Wind shear can be found near weather fronts and is known to influence storms.

The team ran a computer model with atmospheric data collected in northern Australia and eastern China. They simulated the development of eight deep convective clouds by varying the concentration of aerosols, wind shear, and humidity. Then they examined updraft speed and precipitation.

Storm Forming

In the first simulations, the team found that in scenarios containing strong wind shear, more pollution curbed convection. When wind shear was weak, more pollution produced a stronger storm. But convection also changed depending on humidity, so the team wanted to see which effect — wind shear or humidity — was more important.

The team took a closer look at two cloud-forming scenarios: one that ended up with the strongest enhancement in updraft speed and one with the weakest. For each scenario, they created a humid and a dry condition, as well as a strong and weak wind shear condition. The trend in the different conditions indicated that wind shear had a much greater effect on updraft strength than humidity.

When the team measured the expected rainfall, they found that the pattern of rainfall followed the pattern of updraft speed. That is, with strong wind shear, more pollution led to less rainfall. When wind shear was weak, more pollution created stronger storms and more rain — up to a certain point. Beyond a peak level in weak wind shear conditions, pollution led to decreased storm development.

Additional analyses described the physics underlying these results. Water condensing onto aerosol particles releases heat, which contributes to convection and increases updraft speed. The evaporation of water from the cloud droplets cools the air, which reduces the updrafts. In strong wind shear conditions, the cooling effect is always larger than the heating effect, leading to a reduction in updraft speed.

Fault weaknesses, the center cannot hold for some geologic faults

This is a view of the Zuccale Fault, Elba, Italy from a distance. -  Cristiano Collettini, Universita degli Studi di Perugia, Italy,
This is a view of the Zuccale Fault, Elba, Italy from a distance. – Cristiano Collettini, Universita degli Studi di Perugia, Italy,

Some geologic faults that appear strong and stable, slip and slide like weak faults. Now an international team of researchers has laboratory evidence showing why some faults that “should not” slip are weaker than previously thought.

“Low-angle normal faults — faults that dip less than 45 degrees — are a problem,” said Chris Marone, professor of geosciences, Penn State. “Standard analysis shows that these faults should not slip because it is easier to form a new fault than to slip on this orientation.”

However, field evidence shows that low-angle normal faults do slip. One explanation is that they act more like weak faults, slipping and sliding. Previous laboratory experiments indicated that the fabric of the rocks in the fault had too much friction for the faults to slide easily. The researchers wanted to test the material in the fault in a form closer to what occurs naturally.

“The standard way to test the friction of the rocks in a fault is to take some of the rock and grind it up into a powder,” said Marone. “The powder is then tested in an apparatus that applies shear forces to the materials measuring the amount of force it would take to move sides of the fault.”

These conventional measurements indicated that low-angle normal faults have too much friction to move, but the reality is that they do move.

” Cristiano was insistent on checking the shear forces under conditions as close to the natural situation as possible,” said Marone. “I thought what he wanted to do was impossible because the rocks cannot easily be cut into a shape that we can work with. We need a prismatic wafer of the material.”

Cristiano Collettini, researcher at Geologia Strutturale e Geofisica, Universita degli Studi di Perugia, Italy, got his way because of an unusual low-angle normal fault on the Isle of Elba. The Zuccale fault sits exposed on the beach so it is easy to gather large amounts of rock.

The researchers first ground the material and tested the powder in the conventional way. The ground powder did produce sufficient frictional forces to prevent slipping. This is what they expected.

“Normally the rock we use from fault zones comes from below the surface and we only get small amounts to work with,” said Marone. “With the samples from Elba we could use a had rotary cutter and carve a wafer from the rock with the same orientation that would slip in the ground.”

The wafers were about two by two inches square and an eighth of an inch thick. The researchers found that material prepared in this way was very weak when sheared in one direction moving almost like a deck of cards pushed in opposing directions.

The reason for the low friction is small patches of talc and clays like montmorillonite that allow the material to slide.

The researchers, who also include Andre Niemeijer, former Penn State postdoctoral fellow now at Instituto Nazionale Di Geofisica Vulcanologia, Rome, and Cecilia Viti, Universita degli Studi di Siena, Italy, note in today’s (Dec. 17) issue of Nature that “fault weakness can occur in cases where weak mineral phases constitute only a small percentage of the total fault rock and that low friction results from slip on a network of weak phyllosilicate-rich surfaces that define the rock fabric.”

Talc and these clays are often found in fault materials. In areas where connected layers of these materials occur, geologists understood that the connections created weak fabric and slipped easily. But when clays or talc create intermittent flake-like surface coatings, they provide far more slip than when they are simply powdered. The discontinuous flakes and coatings that the researchers found were previously considered insufficiently complete to weaken the fault.

“These low-angle normal faults do not look like they will do anything but creep along, but they could have earthquakes,” said Marone. “There are places in central Italy, for example, where faults like this have had small earthquakes.

ROV images the discovery of the deepest explosive eruption on the sea floor

Oceanographers using the remotely operated vehicle (ROV) Jason discovered and recorded the first video and still images of a deep-sea volcano actively erupting molten lava on the seafloor. Jason, designed and operated by WHOI for the National Deep Submergence Facility, utilized a prototype, high-definition still and video camera to capture the powerful event nearly 4,000 feet below the surface of the Pacific Ocean, in an area bounded by Fiji, Tonga and Samoa.
Oceanographers using the remotely operated vehicle (ROV) Jason discovered and recorded the first video and still images of a deep-sea volcano actively erupting molten lava on the seafloor. Jason, designed and operated by WHOI for the National Deep Submergence Facility, utilized a prototype, high-definition still and video camera to capture the powerful event nearly 4,000 feet below the surface of the Pacific Ocean, in an area bounded by Fiji, Tonga and Samoa.

Oceanographers using the remotely operated vehicle (ROV) Jason discovered and recorded the first video and still images of a deep-sea volcano actively erupting molten lava on the seafloor.

Jason, designed and operated by the Woods Hole Oceanographic Institution for the National Deep Submergence Facility, utilized a prototype, high-definition still and video camera to capture the powerful event nearly 4,000 feet below the surface of the Pacific Ocean, in an area bounded by Fiji, Tonga and Samoa.

“I felt immense satisfaction at being able to bring [the science team] the virtual presence that Jason provides,” says Jason expedition leader Albert Collasius, who remotely piloted the ROV over the seafloor. “There were fifteen exuberant scientists in the control van who all felt like they hit a home run. “

Collasius led a team that operated the unmanned, tethered vehicle from a control van on the research vessel and used a joystick to “fly” Jason over the seafloor to within 10 feet of the erupting volcano. Its two robotic arms collected samples of rocks, hot spring waters, microbes, and macro biological specimens.

Through its fiber optic tether, ROV Jason transmitted-high definition video of
the eruption as it was occurring. The unique camera system, developed and operated by the Advanced Imaging and Visualization Lab at WHOI, was installed on Jason for the expedition to acquire high quality imagery of the seafloor. The AIVL designs, develops, and operates high resolution imaging systems for scientific monitoring, survey, and entertainment purposes. AIVL imagery has been used in several IMAX films and hundreds of television programs and documentaries.

The video from the research expedition, which departed Western Samoa aboard the RV Thomas Thompson on May 5, 2009, was shown for the first time today at the American Geophysical Union fall meeting in San Francisco.

“Less than 24 hours after leaving port, we located the ongoing eruption and
observed, for the first time, molten lava flowing across the deep-ocean seafloor, glowing bubbles three feet across, and explosions of volcanic rock,” reported Joe Resing, a chemical oceanographer at the University of Washington and NOAA, and chief scientist on the NOAA- and National Science Foundation-funded expedition.

For more than a decade, monitoring systems have allowed scientists to listen for
seafloor eruptions but there has always been a time lag between hearing an
eruption and assembling a team and a research vessel to see it. This has meant
that scientists have always observed eruptions after the fact.

“We saw a lot of interesting phenomena, but we never saw an eruption because it
happens so quickly,” said Robert Embley, a NOAA PMEL marine geologist and co-chief scientist on the expedition. “As geologists, you want to see the process in action. You learn a lot more about it watching the process.”

The scientists involved in the expedition had praise for the people and the technology that helped bring that dream to fruition.

“I don’t think there are too many systems in the world that could do what Jason does,” said Embley. “It takes a good vehicle, but a great group of experienced people to get close [to an eruption], hold station, and have the wisdom to understand what they can and cannot do.”

The Jason team maneuvered the vehicle to give scientists an up-close view of the glowing red vents explosively ejecting lava into the sea- often not more than a few feet away from the exploding lava – and the ability to take samples.

Enhancing the experience was the ability to view the eruption in high-definition video. Designed to operate at depths of up to 7,000 meters, the unique still and video camera system acquired 30-60 still images per second, at the same time generating motion, high def video at 30 frames per second. The system uses a high-definition zoom lens – nearly twice the focal length of Jason’s present standard definition camera — that enables researchers to see up-close details of underwater areas of interest that they otherwise could not see.

“We were lucky to have those cameras on the vehicle. They are important to the science,” said Tim Shank, a WHOI macro-biologist on the expedition. “We use the high def cameras to try to identify species. They allow us to look at the morphology of the animals — some smaller than 3 or 4 inches long.”

“In terms of understanding how the volcano is erupting, the high frame rate lets you stop the motion and look to see what is happening,” said Resing. “You can see the processes better.”

The National Science Foundation funded the installation of the camera system for this expedition. The system is being tested in advance of a permanent upgrade in 2010 to the cameras on Jason as well as the manned submersible Alvin. Maryann Keith, of WHOI’s AIVL, Shank, and other scientists operated the camera system with the assistance of the Jason team during the expedition.

In addition to the benefits to science, the cameras will serve the added purpose of giving the public more access to seafloor discoveries.

“Seeing an eruption in high definition video for the first time really brings it home for all of us, when we can see for ourselves the very exciting things happening on our planet, that we know so little about,” Embley said.